Synthesis of Carbazole Derivatives Including Isoquinoline Skeleton

Abstract

The carbazole derivatives (5a, b and 9a, b) including isoquinoline skeleton were synthesized via bromo or nitro substituted 1, 8-dimethylisoquinoline (1a) and 5, 6-dihydro-4H-benz[de]isoquinoline (lb). The reaction of la with N-bromosuccinimide (NBS) in concentrated sulfuric acid gave the 5-bro mo compound 2a, which was subjected to Ullmann reaction with acetanilide in the presence of copper, iodine and potassium carbonate to give the 5-acetamide derivative 3a. Then 3a was subjected to hydrolysis in hydrochloric acid to provide the anilino derivative 4a, and finally, the carbazole derivative 5a was obtained by heating 4a in acetic acid in the presence of palladium acetate. The carbazole derivative 5b was prepared from lb by the same procedures.
On the other hand, the reaction of la with potassium nitrate in concentrated sulfuric acid gave the 5nitro compound 6a, which was reduced in hydrochloric acid by tin (II) chloride to provide the amine 7a. Then, the diazotization of 7a with sodium nitrite followed by the reduction with tin (II) chloride gave hydrazine 8a. Finally, the reaction of 8a with cyclohexanone in methanol provided the carbazole derivative 9a. The carbazole derivative 9b was prepared from lb by the same procedures.